Method for Production of Sputtering Targets

Technical Field

This invention relates to a technology used to a method for production of sputtering targets by spraying method -"Cold dynamic spray".

Background Art

Sputtering targets are used, in particular, for applying metallic or oxide layers in large-area glass manufacturing processes, in engineering and automotive manufacturing industries for producing decorative or functional layers and in processes of manufacturing advanced electro-technical parts.

Presently, sputtering targets are manufactured by conventional metallurgical techniques, either by powder metallurgy as disclosed in the US Pat. Appl. No. 20070086909, wherein the sputtering target is produced by sintering initial metal powder through hot isostatic pressing, or by melting and casting afterwards in an appropriate form, by thermal plasma spraying, by electric arc or flame or by extrusion manufacturing methods. The object of each of these technologies is to reach the most homogeneous and fine-grained structure. Metallographic grain size is one of the critical factors of the sputtering targets functionality, and it may not exceed 100 microns. In principle it holds true that the smaller the grain in the target, the better the quality of layers sputtered afterwards by it and thus the lifetime and usability achieved by such a target increases, which brings fundamental economic and quality benefits to users of these targets.

It is known from the state of the art that to achieve the requested, final microstructure of sputtering targets manufactured by conventional techniques, it is necessary — after casting or forming — to carry out re-crystallization annealing along with mechanical deformation of the targets. In addition, after manufacture with these technologies, it is generally necessary to attach targets to a support

plate either by soldering, gluing or by mechanical means.

After compaction by pressing, tubular or flat inter-metallic sputtering targets manufactured by powder metallurgy must be subjected to sintering under high temperatures and generally in an inert atmosphere, during which time the density of the produced target reaches, at most, 85 % of the theoretical density of the material used.

Tubular or flat inter-metallic sputtering targets manufactured by thermal spraying from a plasma, arc or flame torch are applied directly to a support tube or plate and after spraying are thermally processed to eliminate internal strains arising from the sprayed material and between the applied layer and the support. This method results in grain-growth in a product manufactured in this way and, in addition, the practical density of the target can reach up to 90 % of its theoretical density.

Disclosure of Invention

The shortcomings mentioned above are eliminated with the subject of this invention, which is a method for production of sputtering targets by spraying - "Cold Dynamic Spray", comprising the acceleration of powdered metals, their alloys or mixtures with other metals and metal oxides or pure metal oxides (with ceramics) to speeds exceeding 500 m/s, ensuring sufficient plastic deformation and bonding of powder particles and inpact on the support surface. At the same time, this technology makes it possible to renovate used targets by supplementing the sputtered parts in the existing layer and thus enabling their problem-free recycling and repeated use.

The Cold Dynamic Spray method utilises particles' ability to undergo plastic deformation upon impact on the support material surface and to consequently fuse together, when they exceed the critical speed, which is usually 500 m/s. High- pressure device enabling oriented particle flow has been developed to achieve

supersonic particle speed. Helium, nitrogen or air is normally used as the carrying, i.e., accelerating, gas and the great benefit of this new technology, as opposed to thermal spraying of layers, is the fact that deposition takes place under low temperatures of up to approx. 600 ⁰ C, depending on the type of material used for spraying, whereby the generation of mechanical strains inside the forming layer are prevented.

The aim of this invention is, specifically, a method for producing tubular or planar sputtering targets by spraying powdered metals or mixtures of powdered metals onto support material through a spray method -"Cold Dynamic Spray".

In accordance with the invention, metal is intended to mean any element in the periodic table of elements, having the characteristics of a metal.

Another embodiment of this invention is the fact that powdered material comprises powdered alloys of metals, and this can include any metal that forms alloys.

Another specific embodiment of this invention is the fact that powdered material comprises mixtures of pure powdered metals or powdered alloys with powdered metal oxides.

Yet another embodiment comprises the powdered material made up of mixtures of powdered metal oxides and their mixtures.

In the sense of this invention, metal oxides are intended to mean compounds of any element in the periodic table of elements, having metal properties with oxygen.

According to the invention the method comprises spraying powdered materials, when velocity of individual powder particles reaches a speed of 500-1500 m/s, preferably a speed of 600-1000 m/s by using gas flow helium (He), nitrogen (N ₂ ) or air, while powder with high kinetic energy undergoes plastic deformation on impact against support material, i.e., a tube in the case of tubular sputtering

targets or a planar form in case of planar sputtering targets, bonds and forms a layer of desired thickness.

Metals, in particular steel, glass, plastics, and paper may serve as the support material (carrier).

This method allows to produce sputtering targets with different thicknesses of the sputtered material layer, varying from 5 microns up to an unlimited layer thickness, typically up to 100 to 300mm, while eliminating the necessity of mechanical forming and thermal processing to achieve the required target structure. According to the invention, no mechanical strains appear between the support plate and the sprayed target, and a fine-grained structure is formed that can be easily directed by selecting a suitable granulometry of the sprayed powder.

In comparison with thermal spraying processes used for production of sputtering targets, the significant advantage of the Cold Dynamic Spray rests in the form of a compact, homogeneous layer that is free from any internal mechanical strains, eliminating the need for any subsequent annealing and resulting in substantial savings in manufacturing expenses as well as increased quality of targets made in this way, which have a fine crystalline structure determined by selecting the powder grain size and reaching a density of 99 %, in comparison with the theoretical density of the material used for spraying, and with a target volume porosity of less then 0.5 %.

Another advantage of sputtering targets manufactured by Cold Dynamic Spraying is a uniform, fine-grained isotropic structure, which ensures, in contrast with other manufacturing methods, identical characteristics of the target in all its parts, and these characteristics can be easily controlled through the selection of appropriate parameters of the sprayed powder.

According to the invention, it was also found out, that by using the Cold Dynamic Spray method, it is possible to achieve the required structural parameters directly, during the process of forming the basic shape of the target, which eliminates costly

operations of mechanical forming and annealing. At the same time, the Cold Dynamic Spraying enables production time to be reduced by 30 %.

A substantial advantage of the described cold spraying method lies in the fact that it completely eliminates the aforementioned operations of fixing a target onto a support plate, as the target is formed directly onto the base plate, whereby the target is bonded with the support plate through plastic deformation brought on by impacting particles of the target powdered material.

Another benefit of this invention is the fact, that the Cold Dynamic Spray method, in comparison with the above state of the art, facilitates manufacturing processes of inter-metallic targets with a density of at least 99 % of the theoretical density of the given material, which again positively impacts the quality of the sprayed coating and the target lifetime.

Brief Description of Drawing

The Invention will be explained in more detail with a drawing, illustrating in Figure 1 a metallurgical cut-out taken from a target; it is apparent that its grain is less than 32 microns.

Examples

The objective of the following examples is to illustrate the subject of this invention, while the given examples should in no way limit the scope of the invention, which is defined in the appended patent claims.

Example 1

To manufacture a tubular target, 25 000 g of silver powder was used, with a purity of 99.99 % and grain sizes ranging from 1 to 32 microns, obtained by sieving of

the entering raw material. A steel tube, 115 mm in diameter and made of AISI316L material blasted by alumina powder was used as the support material. A silver target, i.e., a silver layer with uniform thickness of 22 mm was formed in the course of eight hours on the steel support tube by application of the Cold Dynamic Spray method, with supersonic particle speed and 380 ⁰ C in temperature. Afterwards, a metallurgical cut-out was made from a section of the target as shown in Figure 1. It is apparent from the illustration, that the grain size of the target is less than 32 microns, while porosity is less than 0.5 %. Then the target was subjected to sputtering and an evaluation was made by comparing it with a silver reference target manufactured by casting and subsequent forming followed by heat treatment. Lifetime of the target manufactured by the Cold Dynamic Spray method was 16 % longer.

Example 2

To manufacture a planar target, 20 000 g of zinc alloy powder was used, containing 2 % of aluminium with a purity of 99.99 % and grain sizes ranging from 1 to 32 microns, obtained by sieving the entering raw material. A steel plate made of AISI316L material blasted with alumina powder and coated with a graphite separation layer was used as the support material. Over a five-hour period, a Zn target containing 2 % aluminium, i.e., a ZnAI2 layer with a uniform, 10 mm thickness was formed on the support steel plate by the Cold Dynamic Spray method, with supersonic particle speed and 250 ⁰ C in temperature. Porosity of the target was less than 0.25 %. Afterwards, the target was subjected to sputtering and an evaluation was made by comparing it with a ZnAI2 reference target manufactured by a plasma spraying method with heat treatment. Lifetime of the target manufactured by the Cold Dynamic Spray method was longer by 10 %.

Example 3

To manufacture a tubular target, 9 300 g of nickel powder was used, with a purity of 99.99 % and grain sizes ranging from 1 to 80 microns and 700 g of vanadium

powder with a purity of 99.99 % and grain sizes ranging from 1 to 32 microns obtained by sieving of the entering raw material. A steel plate with a size of 100x300mm, made of AISI316L material blasted with alumina powder was used as the support material. Over a four hour period, the Ni target containing 7 % of vanadium, i.e., an NiV7 layer with uniform thickness of 38.7 mm was formed on the support steel plate with the Cold Dynamic Spray method, with supersonic particle speed and 300 ⁰ C in temperature. Porosity of the target was less than 0.30 %. Afterwards, the target was subjected to sputtering and an evaluation was made by comparing it with a ZnA12 reference target manufactured by a plasma spraying method with heat treatment. Lifetime of the target manufactured by the Cold Dynamic Spray method was longer by 12 %.

Example 4

To manufacture a tubular target, 15 000 g of TiO ₂ powder was used, with a purity of 99.99 % and grain sizes ranging from 1 to 32 microns and 750 g of Ti powder with a purity of 99.99 % and grain sizes ranging from 1 to 32 microns. A steel tube 115 mm in diameter, made of AISI316L material blasted with alumina powder was used as the support material. Over a six-hour period, the TiO _{1 9} target, i.e., a TiO ₂ + Ti layer with uniform thickness of 20 mm was formed on the support steel tube by the Cold Dynamic Spray method, with supersonic particle speed and 380 ⁰ C in temperature. Porosity was less than 0.25 %. Afterwards, the target was subjected to sputtering and an evaluation was made by comparing it with a TiOi ₉ reference target manufactured by a plasma spraying method with subsequent heat treatment. Lifetime of the target manufactured by the Cold Dynamic Spray method was longer by 14 %.

Example 5

To manufacture a tubular target, 5 000 g of TiO ₂ powder was used, with a purity of 99.99 % and grain sizes ranging from 1 to 32 microns and 5 000 g of Ti powder with a fineness of 99.99 % and grain sizes ranging from 1 to 32 microns. A steel

tube 115 mm in diameter, made of AISI316L material blasted with alumina powder was used as the support material. Over a five-hour period, the TiO target, i.e., a TIO2 ⁺ Ti layer with uniform thickness of 10 mm was formed on the support steel tube with the Cold Dynamic Spray method, with supersonic particle speed and 360 ⁰ C in temperature. Porosity was less than 0.35 %. Afterwards, the target was subjected to sputtering and an evaluation was made by comparing it with a TiO reference target manufactured by a plasma spraying method and subsequent heat treatment. Lifetime of the target manufactured by the Cold Dynamic Spray method was longer by 15 %.

Industrial Applicability

Sputtering targets manufactured by the Cold Dynamic Spray method, disclosed in this invention, may replace sputtering targets manufactured by conventional technologies.